Refrigeration cycle apparatus

ABSTRACT

An object of the present invention is to provide a refrigeration cycle apparatus having a compressor that is not easily heated to high temperature by sliding heat and thus higher in reliability. 
     Provided is a refrigeration cycle apparatus having a cost-effective compressor in the configuration in which a piston  9  eccentrically revolving, as driven by a shaft  4,  is placed in a cylinder  6  and the circular terminal region  10   a  of a vane  10  partitioning the cylinder  6  into a suction chamber  12  and a compression chamber  13  is connected slidably to the external surface of the piston  9  in surface contact, which can reduce the sliding heat and is thus resistant to deterioration in reliability by reaction of the operating refrigerant.

TECHNICAL FIELD

The present invention relates to a high-reliability refrigeration cycle apparatus, such as room air conditioner, refrigerator or air conditioning apparatus, using a refrigerant mainly containing a chlorine atom-free low-global warming potential hydrofluoroolefin having a carbon-carbon double bond as its operating refrigerant and employing a rotary compressor as its compressor.

BACKGROUND ART

The operating refrigerants used in conventional refrigeration cycle apparatuses are shifting to HFC (hydrofluorocarbon) compounds having zero ozone depletion potential, but these HFC-based refrigerants are also causing a problem recently, because they have very high global warming potential. Thus, refrigeration cycle apparatuses using a refrigerant mainly containing chlorine atom-free low-global warming potential hydrofluoroolefin having a carbon-carbon double bond have been studied. Lubricant materials for this kind of rotary compressors used with conventional HFC-based refrigerants have been modified in various ways to assure reliability (see, for example, Patent Document 1).

FIG. 5 is a crosssectional view of a rotary compressor used with the conventional HFC (hydrofluorocarbon)-based refrigerant described in Patent Document 1. In the configuration, a piston 43 is inserted along the internal surface of a cylinder 41 and revolves with revolution of a shaft 42, and a refrigerant gas is suctioned and compressed respectively in a suction chamber 45 and a compression chamber 46 partitioned by a vane 44. Obviously from its mechanical configuration, the areas of the rotary compressor abraded most intensively are where the terminal region of the vane 44 and the external surface of the piston 43 are in contact with each other, and high discharge pressure is applied to a rear face of the vane 44, the end of the vane 44 is pressed onto the external surface of the piston 43 by line contact, intensively by the pressure difference between the discharge pressure and the pressure in the cylinder, leading to increase in surface pressure and boundary lubrication. In addition, the vane was subjected to nitridation treatment or CrN or TiN ion plating on the surface, for improvement of its abrasion resistance and assurance of reliability.

FIG. 6 is a crosssectional view illustrating a swing rotary compressor used with the conventional HFC (hydrofluorocarbon)-based refrigerant described in Patent Document 2. It is a swing rotary compressor having a piston 53 consisting of a roller 53 a and a vane 54 formed as integrated with the roller 53 a. In the configuration, the vane 54 is held slidably between two semi-cylindrical sliding parts 57 in a cylindrical hole unit 51 a formed outside the internal surface of a cylinder 51; the piston 53 is inserted into the cylinder 51 from the internal surface for movement thereof by revolution of a shaft 52, and the refrigerant gas is suctioned and compressed respectively in a suction chamber 55 and a compression chamber 56 partitioned by the vane 54.

Because the roller 53 a and the vane 54 are formed as an integrated structure in the swing rotary compressor, differently from the rotary compressor described in Patent Document 1, the vane terminal region and the piston external surface are not in contact with each other, and the semi-cylindrical sliding parts and the cylindrical hole unit 51 a formed in the cylinder 51 are in surface contact with each other, and thus, the sliding state is relaxed.

CITATION LIST

-   Patent Document 1: JP-A 11-236890 -   Patent Document 2: JP-A 2003-106692

SUMMARY OF INVENTION Technical Problem

However, when a rotary compressor of refrigeration apparatus using a refrigerant mainly containing a chlorine atom-free low-global warming potential hydrofluoroolefin having a carbon-carbon double bond is considered, there was a problem, under severe environment at high temperature because of the sliding heat caused by boundary lubrication, particularly because the surface pressure is raised, as the vane terminal region and the piston external surface are pressed in line contact, that hydrogen fluoride is generated in reaction with the refrigerant and thus, abrasion of the vane terminal region and the piston external surface is accelerated and the refrigeration oil is decomposed, leading to decrease in reliability. When the configuration of swing compressor is employed, the contact changes from line contact to surface contact, leading to relaxation of sliding, but, because the piston has an integrated structure of roller and vane, it was very expensive to produce it at high accuracy. Because two sliding parts demanding severe processing accuracy are needed additionally, the increase in the number of parts also led to increase in production cost.

An object of the present invention, which was made to solve the problems of traditional technology, is to provide a cost-effective compressor that is resistant to decomposition of its refrigerant, as the sliding heat is reduced by alteration of the contact between the vane terminal region and the piston external surface from line contact to surface contact, and thus, assures reliability of the compressor and yet retains the configuration of conventional rotary compressors as much as possible.

Solution to Problem

The refrigeration cycle apparatus according to the present invention, which achieved the object above, has therein a rotary compressor using a single refrigerant of a hydrofluoroolefin having a carbon-carbon double bond or a mixed refrigerant containing the hydrofluoroorefin as the primary component and hydrofluorocarbons having no double bond as the operating refrigerant and having a piston eccentrically revolving, as driven by a shaft, in a cylinder, the terminal region of a vane, which partitions the cylinder into a suction chamber and a compression chamber, being slidably connected to the external surface of the piston.

It is possible in this way to reduce generation of hydrogen fluoride that occurs when the refrigerant reacts with water and oxygen, because, in the rotary compressor, the vane terminal region is slidably connected to the piston external surface, leading to change from severe boundary lubrication state of line contact to surface contact lubrication state and the sliding parts are not heated significantly.

Because, in the rotary compressor, the vane terminal region is slidably connected to the piston external surface, leading to change from severe boundary lubrication state of line contact to surface contact lubrication state and the sliding parts are not heated significantly, it is possible in the refrigeration cycle apparatus according to the present invention to reduce generation of hydrogen fluoride that occurs when the refrigerant reacts with water and oxygen and to provide a high-reliability refrigeration cycle apparatus by using a refrigerant mainly containing a chlorine atom-free low-global warming potential hydrofluoroolefin having a carbon-carbon double bond.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a chart showing the system configuration of the refrigeration cycle apparatus in embodiment 1 of the present invention.

FIG. 2 is a vertical crosssectional view of the rotary compressor in embodiment 1 of the present invention.

FIG. 3 is a side crosssectional view of the compression mechanism unit in the same rotary compressor.

FIG. 4 is a figure showing the relationship between the global warming potential of two-component mixture refrigerants and the blending ratio.

FIG. 5 is a side crosssectional view illustrating the compression mechanism unit of a traditional rotary compressor.

FIG. 6 is a side crosssectional view illustrating the compression mechanism unit of a traditional swing rotary compressor.

DESCRIPTION OF EMBODIMENTS

The first aspect of the invention, which relates to a refrigeration cycle apparatus, comprising a rotary compressor, using a single refrigerant of a hydrofluoroolefin having a carbon-carbon double bond or a mixed refrigerant containing the hydrofluoroolefin as the primary component and hydrofluorocarbons having no double bond as the operating refrigerant and having a motor and a compression mechanism unit with a shaft driven by a rotor of the motor in a tightly sealed container, the compression mechanism unit having a piston eccentrically revolving, as driven by a shaft, in a cylinder, the terminal region of a vane, which partitions the cylinder into a suction chamber and a compression chamber, being slidably connected to the external surface of the piston, a condenser cooling the refrigerant gas pressurized, as compressed by the compressor, a throttling mechanism depressurizing the high-pressure refrigerant liquefied by the condenser, and a vaporizer gasifying the depressurized liquid refrigerant, which are connected to each other with piping. It is thus possible to reduce heating of the sliding face and suppress generation of hydrogen fluoride by decomposition of the refrigerant, because the contact between the vane terminal region and the piston external surface of the rotary compressor changes from severe line contact to slidable connection. It is also possible to suppress abrasion of the vane and the piston and provide a refrigeration cycle apparatus higher in reliability by suppressing generation of hydrogen fluoride.

The second aspect of the invention, which relates to the refrigeration cycle apparatus of the first aspect of the invention wherein the terminal region of the rotary compressor vane and the external surface of the piston are slidably connected to each other, by the circular terminal region of the vane and the arc-shaped slot on the external surface of the piston, can reduce temperature rise by sliding, because the connecting parts are both arc-shaped and the contact becomes surface contact.

The third aspect of the invention which relates to the refrigeration cycle apparatus of the second aspect of the invention wherein the angle of connection of the arc-shaped slot on the external surface of the piston to the circular terminal region of the vane is 180° or more, can suppress separation of the connecting parts and also can expand the contact area, thus reducing surface pressure and temperature rise by sliding.

The fourth aspect of the invention, which relates to the refrigeration cycle apparatus of the first to third aspects of the invention, wherein the hydrofluoroolefin is a mixed refrigerant containing tetrafluoropropene as the primary component and two or three hydrofluorocarbons having no double bond, such as difluoromethane, pentafluoroethane and tetrafluoroethane, added thereto at a rate to give a global warming potential of 5 or more and 750 or less, desirably 350 or less, can improve efficiency and minimize the influence on global warming as much as possible, even when the unrecovered refrigerant is discharged into air.

The fifth aspect of the invention, which relates to the refrigeration cycle apparatus of the first to fourth aspects of the invention, wherein the refrigeration oil is a synthetic oil containing an oxygen-containing organic compound selected from the group consisting of polyoxyalkylene glycols, polyvinylethers, copolymers of poly(oxy)alkylene glycols or the monoether thereof and polyvinylether, polyol esters and polycarbonates as the principal component, or a synthetic oil containing an alkyl benzene or an α-olefin as the principal component, can provide a high-reliability refrigeration cycle apparatus.

Hereinafter, favorable embodiments of the present invention will be described with reference to drawings. However, it should be understood that the present invention is not restricted by these embodiments.

Embodiment 1

FIG. 1 is a chart showing the system configuration of the refrigeration cycle apparatus in the first embodiment of the present invention.

As shown in FIG. 1, the refrigeration cycle apparatus of the present embodiment, when explained for example as a refrigeration cycle primary for air conditioning, mainly has a compressor 61, a condenser 62, a throttling mechanism 63 and a vaporizer 64, and these devices are connected to each other via a set of piping so that the refrigerant circulates in the system.

In addition, the refrigeration cycle apparatus contains a refrigerant mainly containing a chlorine atom-free low-global warming potential hydrofluoroolefin having a carbon-carbon double bond sealed therein. The refrigerant sealed in the refrigerating apparatus is a two- or three-component mixed refrigerant containing a hydrofluoroolefin, such as containing tetrafluoropropene (HFO1234yf) as the primary component, and additionally one or more hydrofluorocarbon selected from the group consisting of difluoromethane (HFC32), pentafluoroethane (HFC125) and tetrafluoroethane (R134a), which are added thereto at a rate to give a global warming potential (GWP) of 4 or more and 750 or less, desirably 4 or more and 300 or less. It may be a single refrigerant of hydrofluoroolefin (GWP=4).

FIG. 4 is a figure showing the relationship between the global warming potential of a two-component mixture refrigerant of tetrafluoropropene and difluoromethane or pentafluoroethane and the blending ratio. Specifically as shown in FIG. 4, in the case of a two-component mixture, when tetrafluoropropene and difluoromethane are mixed, the blending rate of difluoromethane should be 44 wt % or less, to give a GWP of 300 or less; alternatively when tetrafluoropropene and pentafluoroethane are mixed, the blending rate of pentafluoroethane should be 21.3 wt % or less, to give a GWP of 750 or less; and the blending rate of pentafluoroethane should be 8.4 wt % or less, to give a GWP of 300 or less.

When the refrigerant is a single refrigerant of tetrafluoropropene, it has a quite favorable GWP value of 4. However, it has a specific volume larger and thus a refrigerating capacity lower than those of the refrigerants mixed with hydrofluorocarbons and, for that reason, demands a larger-scale cooling cycle apparatus. In other words, it is possible to improve the certain properties such as refrigerating capacity and make the refrigerant more easily usable, compared to a single refrigerant of hydrofluoroolefin, by using a mixed refrigerant containing the hydrofluoroolefin having a carbon-carbon double bond as the primary component and the hydrofluorocarbons having no double bond. Thus, the amount of the tetrafluoropropene in the refrigerant sealed therein, including the case of a single refrigerant, may be selected arbitrarily according to the applications such as the cooling cycle apparatus into which the compressor is incorporated and the conditions such as the restriction on GWP described above.

It is possible in this way to minimize the influence on global warming as much as possible, even when the unrecovered refrigerant is discharged into air. The mixed refrigerant at the rate above has a smaller temperature difference and a behavior closer to a pseudo-azeotropic mixed refrigerant, even though it is a non-azeotropic mixed refrigerant, and thus, can improve the cooling capacity and the cooling capacity coefficient (COP) of the cooling cycle apparatus.

In the refrigeration cycle apparatus in the configuration above, the refrigerant is converted to liquid by pressurization and cooling and to gas by depressurization and heating. The compressor 61, which is driven by a motor, pressurizes a low-temperature low-pressure gas refrigerant into a high temperature high-pressure gas refrigerant and feeds the gas into the condenser 62. The gas is condensed in the condenser 62, as it is cooled by air blown for example from a fan, and gives a low-temperature high-pressure liquid refrigerant. The liquid refrigerant is depressurized by the throttling mechanism 63, giving partially a low-temperature low-pressure gas refrigerant and a low-temperature low-pressure liquid refrigerant, and feeds the liquid refrigerant into the vaporizer 64. The liquid refrigerant is vaporized in the vaporizer 64, as heated by air blown for example form a fan, giving a low-temperature low-pressure gas refrigerant, which is then suctioned into the compressor 61 and pressurized therein. In this way, liquefaction and gasification is repeated therein in the cycle described above.

Although the refrigerating apparatus was described as a refrigeration cycle apparatus primarily for air conditioning in the embodiment above, it is of course possible to operate it as a heating cycle apparatus for example by using a four-way valve.

FIG. 2 is a vertical crosssectional view of the rotary compressor used in the refrigeration cycle apparatus shown in FIG. 1. A stator 2 a of a motor 2 is connected to the upper region of a tightly sealed container 1, and a compression mechanism unit 5 having a shaft 4 driven by a rotor 2 b is connected to the lower region of the tightly sealed container 1. A top bearing 7 is connected to the top end of the cylinder 6 of the compression mechanism unit 5 and a bottom bearing 8 to the bottom end thereof, for example with screws. In the cylinder 6, a piston 9 is inserted into the eccentric region 4 a of the shaft 4 for eccentric revolution. In addition, a refrigeration oil is stored in the bottom region of the tightly sealed container 1, and the refrigeration oil is desirably an oil miscible with the refrigerant and contains at least one oxygen-containing organic compound selected from the group consisting of polyoxyalkylene glycols, polyvinylethers, copolymers of poly(oxy)alkylene glycols or the monoethers thereof and polyvinylether, polyol esters and polycarbonates as the principal component, and additionally, as needed, various additives such as extreme-pressure lubricants, oils, antioxidants, acid scavengers and antifoams are added. However, in small-scale cooling cycle apparatuses such as home air conditioners, it is practically possible to use a refrigeration oil not miscible with the refrigerant, such as alkylbenzene or α-olefin, if the flow rate of the refrigerant in piping is high enough.

FIG. 3 is a crosssectional view of the compression mechanism unit of the rotary compressor shown in FIG. 2. As shown in FIG. 3, a vane 10 is inserted into the vane groove 6 a of cylinder 6 and the circular terminal region 10 a of the vane 10 is slidably connected to the arc-shaped slot 9 a on the external surface of the piston 9.

Hereinafter, the operation and action of the rotary compressor in the configuration above will be described.

First, a mixed refrigerant gas containing a hydrofluoroolefin having a carbon-carbon double bond as the primary component and hydrofluorocarbons having no double bond or a single refrigerant gas of a hydrofluoroolefin having a carbon-carbon double bond is suctioned into a suction chamber 12 through a suction hole 11 formed in the cylinder 6. The gas refrigerant in the compression chamber 13 is compressed by the leftward revolution of the piston 9 (arrow direction) and ejected through a discharge slot 14 out of the discharge outlet (not shown in the Figure). The compressed gas refrigerant discharged into the tightly sealed container 1 is then fed though the gap of the motor 2 and discharged out of a discharge pipe 15 formed in the upper region of the tightly sealed container 1, together with the refrigeration oil mist present in the surrounding region.

Although a high-pressure discharge pressure and a large force by the pressure difference with the pressure in the cylinder is applied to the rear face 10 b of the vane 10 in the present invention, the vane is in surface contact, not in conventional line contact, with the piston and thus, is not exposed to severe environment at high temperature caused by sliding friction, because the circular terminal region 10 a of the vane 10 is slidably connected to the arc-shaped slot 9 a formed on the external surface of piston 9. Because the sliding face is less easily exposed to high temperature, it is possible to reduce generation of hydrogen fluoride by decomposition of the mixed refrigerant gas containing a hydrofluoroolefin having a carbon-carbon double bond as the primary component and hydrofluorocarbons having no double bond or a single refrigerant gas of a hydrofluoroolefin having a carbon-carbon double bond.

When the angle of the connection between the circular terminal region 10 a of the vane 10 and the arc-shaped slot 9 a on the external surface of the piston 9 is 180° or more, it is possible to suppress separation of the connecting parts and also can expand the contact area, thus reducing the surface pressure and the temperature rise by sliding.

Further because the rotary compressor of the refrigeration cycle apparatus according to the present invention is different only, mainly in the shape of the vane and the piston from conventional rotary compressors, and thus, it is possible to produce it cost-effectively without major alteration of production facility.

INDUSTRIAL APPLICABILITY

As described above, the rotary compressor according to the present invention can assure the reliability of the refrigeration cycle apparatus, even when a mixed refrigerant containing a hydrofluoroolefin having a carbon-carbon double bond as the primary component and hydrofluorocarbons having no double bond is used, and thus, can be used in applications such as water-heating apparatuses, car air-conditioning units, refrigeration cycles and dehumidifier systems. 

1. A refrigeration cycle apparatus, comprising: a rotary compressor, using a single refrigerant of a hydrofluoroolefin having a carbon-carbon double bond or a mixed refrigerant at least containing the hydrofluoroolefin and additionally hydrofluorocarbon having no double bond as an operating refrigerant and having a motor and a compression mechanism unit driven by a rotor of the motor in a tightly sealed container, the compression mechanism unit having a piston eccentrically revolving, as driven by a shaft, in a cylinder, the terminal region of a vane, which partitions the cylinder into a suction chamber and a compression chamber, being slidably connected to the external surface of the piston; a condenser cooling the refrigerant gas pressurized, as compressed by the compressor; a throttling mechanism depressurizing the high-pressure refrigerant liquefied by the condenser; and a vaporizer gasifying the depressurized liquid refrigerant, wherein the rotary compressor, the condenser, the throttling mechanism and the vaporizer are connected to each other with piping.
 2. The refrigeration cycle apparatus according to claim 1, wherein the terminal region of the rotary compressor vane and the external surface of the piston are slidably connected to each other, by the circular terminal region of the vane and an arc-shaped slot on the external surface of the piston.
 3. The refrigeration cycle apparatus according to claim 2, wherein the angle of connection of the arc-shaped slot is 180° or more.
 4. The refrigeration cycle apparatus according to claim 1, wherein the operating refrigerant is a two- or three-component mixed refrigerant containing a hydrofluoroolefin tetrafluoropropene (HFO1234yf) as primary component, and one or more hydrofluorocarbon having no double bond and selected from the group consisting of difluoromethane, pentafluoroethane and tetrafluoroethane, the hydrofluorocarbon being added at a rate to give a global warming potential of 5 or more and 750 or less.
 5. The refrigeration cycle apparatus according to claim 1, wherein the refrigeration oil is a synthetic oil containing an oxygen-containing compound selected from the group consisting of polyoxyalkylene glycols, polyvinylethers, copolymers of poly(oxy)alkylene glycols or the monoethers thereof and polyvinylether, polyol esters and polycarbonates as a principal component or a synthetic oil containing an alkyl benzene or an α-olefin as a principal component. 